Portable grinding tool



April 10, 1956 J. R. TENNEY PORTABLE GRINDING TOOL.

3 Sheets-Sheet 1 Filed June 1, 1955 INVENTOR. JOHN R. TE/VNE), yomzg/@45 his Attorney.

April 10, 1956 TENNEY 2,741,078

PORTABLE GRINDING TOOL Filed June 1, 1955 3 Sheets-Sheet 5 Tug-K '5- 68c 68- 5,8 I P IN VEA/ TOR. 53 JOHN R. TEA/NE),

BK yew/10 his Af/omey.

United States Patent PORTABLE GRINDING TooL John R. Tenney, Salt LakeCity, Utah, assignor to United States Steel Corporation, a corporationNew Application June 1, 1955, Serial No. 512,353

4 Claims. (Cl. 51-244) The present invention relates to grinding toolsand more particularly to a portable grinding tool which can betemporarily positioned adjacent a workpiece to be ground and operatedfrom a remote station.

The tool of the invention finds particular adaptation in use forgrinding or turning commutators of large motors and generators and inthat respect a preferred embodiment of the invention will be described.

During the process of grinding or turning the commutator of a largemotor or generator it is necessary to have the grinding stone heldfirmly and moved back and forth across the face of the commutator as itis rotated. Prior to my invention this operation was accomplished bymeans of a grinding stone carried by a carriage mounted for reciprocalmovement on a lathe bed which was mounted on the brush ring of the motoror generator by means of a jig to extend across the face of thecommutator. The carriage was provided with a manually operated traversefeed and a manually operated cross feed. The tool was operated by aworkman who turned the traverse feed to move the stone across the faceof the commutator, and the cross feed to move the stone inwardly oroutwardly as required. Another workman held the collecting nozzle of avacuum hose adjacent the stone as it reciprocated to pick up copperparticles and abrasive dust that was generated during the grindingoperation. It was necessary for another workman to be stationed at themachine during the grinding operation to trip 01f the motor in the eventof an emergency.

When grinding the commutator of a large motor under power it wasnecessary for the men performing the operation to wear high tensiongloves, and stand on rubber blankets for insulation from the energizedmotor. Respirators and goggles were also worn as safety precautions bythe workmen. The necessity of using all the safety equipment requiredmade the grinding operation extremely awkward and cumbersome. Due to thelength of time required to grind or turn the commutator of a large motoror generator it was necessary to use two crews of men alternately toprevent excessive fatigue and resultant safety hazard.

I propose to eliminate the above described disadvantages inherent incommutator grinding by providing an apparatus including a portablegrinder lathe automatically operated by means of two motor drivesconnected by flexible shafts to the traverse drive and cross feed of thelathe. The apparatus I propose also includes common limit switches forthe traverse drive and cross feed whereby the traverse direction oftravel of the tool carriage is simultaneously indexed to provideautomatic feeding of the grinding stone inwardly in the required amount.The electrical circuit of the apparatus is so arranged that the crossfeed is also actuated automatically whenever a high spot on the face ofthe commutator is encountered. The driving motors of the apparatus ofthe invention are carried in a wheeled cabinet and connected with thetraverse drive and cross feed of the lathe of the invention by means ofelongated flexible shafts so that the lathe can 2,741,078 Patented Apr.10, 1956 be installed on a motor or generatorand be operated at a safedistance. This arrangement makes it possible for the operators to worksafely without the need of special protective clothing and blankets. Thecabinet housing the motors is provided with a control panel fitted withinstrument and switches necessary to the operation of the grinding latheas well as a control switch whereby the motor or generator being groundcan be shut down in the event any trouble develops.

It is accordingly an object of my invention to provide a portablegrinding lathe which includes an automatically operated grinding toolcarriage having powered traverse drive and cross feed, and means wherebythe direction of the traverse drive is automatically reversed and thecross feed is automatically indexed at each terminus of the path oftravel of the carriage.

It is a further object of my invention to provide a device of acharacter described in the object stated above including means wherebythe cross feed is actuated automatically to move the stone inwardlytoward the commutator face when a high spot is encountered thereon.

These and other objects will become more apparent after referring to thefollowing specification and attached drawings, in which:

Figure 1 is a plan view;

Figure 2 is a side elevational view;

Figure 3 is a sectional view taken on the line III-III of Figure 2; and

Figure 4 is a diagrammatic illustration of the electrical system of theinvention.

Reference numeral 2 designates a conventional motor having a commutator4 and a brush holder ring 6. The apparatus of my invention is mounted onthe brush holder ring 6 by means of a jig 8 and bolts 10 and includes alathe bed 12 having tool carriage l4 slidable thereon. The lathe bed 12is mounted across the face of the commutator 4 extending from its oneside to the other. The tool carriage is moved across the face of thecommutator by means of a conventional screw shaft traverse drive 16 andcarries grinding stones 18 supported on a cross feed- Ztv which includesa sliding cross bed 27 and a screw shaft 21 driven by a splined shaft 22and gear 24 splined thereto. The traverse drive shaft 16 is connectedwith the gear head drive 26 of a reversible motor 28 by means of aflexible shaft 30. Splined shaft 22 is connected with the gear headdrive 32 of a motor 34 by means of a flexible shaft 35. Motors 28 and-34are mounted in a cabinet 36 which is located in the vicinity of theequipment being processed but spaced a sufiicient distance therefrom toallow operation of the device of the invention at a safe distance fromthe equipment. The cabinet is provided with wheels 38 so that it can beeasily moved to difierent locations where work is to be performed.Cabinet 36 is also provided with an inclined control panel 49 havingconventional meters and control switches 42 thereon. The control panel4!) is also equipped with a control switch 44 which is connected intothe control circuit (not shown) of motor 2 so that rotation of the motorcommutator can be started or stopped from the control panel.

Limit switches 56 and 48 are mounted on the lathe bed 12 at oppositeends of the path of travel of the carriage 14. Limit switches 46 and 48are adapted to be tripped by the carriage 14 as it reaches each end ofits path of travel to reverse the motor 28 and thereby reverse itsdirection of travel. Each time one of the limit switches is trippedmotor 34 is energized, through means to be described hereinafter, torotate shaft 22 and feed stones 18 inwardly closer to the commutatorready for the next trip across its face. At any time during the traversemotion'of the carriage 14 across the commutator that the torquerequirement on motor 28 increases due to a high spot on the commutatorface, this extra torque requirement'on motor 28 actuates an electricalsensing ci-rcui-t,--to

be described, which causes motor 34 to increase the pressure of stones18 against the commutator to grind oflthe highspot. 7U V lThe nozzle dof a -flexible vacuum hose 52 is carried by the toolcarriage 14 adjacentthe grinding stone 18 for the purpose of picking up particles of metalanddust generated during the grinding operation.

'In operation, the lathe bed 12 is fastened against the commutator 4which is to be ground and secured in position by means of a jig 8clampedto the brush holder ring dby volts 10, as best shown in Figure'3.The cabinet 36 iswheeled into position and the flexible shafts and areinstalled connecting motor '28 and shaft 16, and

motor 3-l-andshaftl22, respectively. Motor 28 is actuated by closing apush button switch 42a on panel 46 to energize a relay '54'havingnormally open contacts 54a and I 54b whereupon contacts'54a and 54b areclosed completing a circuit to a contactor 56 causing its normally opencontacts 56a and 56b to close.

The limit switch also closes the normally open contact 5 3a completing acircuit to a relay 68 causing its normally open contacts 69a and 60b toclose whereupon a contactor 62 having normally open contacts 62a and 62bis energized causing its contacts to close. Closing of contacts 62a and62b causes current to flow from supply line 58 to the. bottom of thearmature of motor 28 thereby reversing its direction and causingcarriage 14 to move toward limit switch 46. closes its own hold circuitthrough normally closed back contact %Z of limit switch 46.

When limit switch 46 is tripped by carriage 14, it opens contact 5-65,de-energizing relay 6i) and, in turn, contactor 52, stopping motor 23.The limit switch also closes normally open contacts 46:1,re-energi2ingrelay 54. The lat- V ter completes its own holding or sealing circuitand energizes contactor 56 to start motor 28 in the same manner asdescribed above when push button 42a'is closed.

A push button 42b is provided on panel 40 in a circuit parallel withlimit switch 43 for starting motor 28 in the direction whereby carriage14 will be moved toward limit switch 46.

Each time motor 28 is started or reversed or a high spot on the surfaceof commutator 4 is encountered by stones 18, a surge of current passesto motor 28. This surge of current causes a voltage impulse across thesecondary winding of a current transformer 64, which, in turn, causes VV Closingof contacts 56a and 56b causes current to flow from power line58' The relay 60, at contact 69a,

4 a signal 'to be *fed into a --magnetic amplifier 66 which thensupplies. current enough to actuate a relay 68 having a normally opencontact68c. The closing of contact 68c shunts a resistance 70 whereuponsufficient voltage.

is applied to motor 34 from power line 58' to energize it for apredetermined time. Energization of 'motor 34 causes cross feed 20 tomove the grinding stones 18 closer to the commutator surface. 7

A master switch 72 is provided in the power lines 58 and 53. This switchis kept open when-the equipment in pcration.

While one embodiment ofmy invention has been shown and described, itwill be apparent that other adaptations and modifications may be madewithout departing from the scope of the following claims.

I claim:

i. A lathe comprising a tool for machining a workpiece, a reciprocatingtool carriage for supporting the tool, a first motor for reciprocatingsaid tool carriage, a second motor for feeding said tool'intotheworkpiece, apair of limit switches one at each end of the path of-travelof said carriage, means operable by said limit switches for reversingthe direction of rotation of said first motor, and nieans operable by asurge in current to said first motor for causing said second motor tofeedfsaid tool towardcarriage mounted on said bed for movement alongsaid.

workpiece, a grinding tool mounted on'said carriage, a first motor forreciprocating said carriage, a second motor for feeding said tool intothe workpiece, a pair of limit switches one at each end of the path oftravel of said carriage, means operable by said limit switches forreversing the direction of rotation of'said first motor, and means Noreferences cited.

